The conventional megawatt-level wind power generation system mainly includes two kinds of wind power generator sets, i.e., a full-power wind power generator set and a doubly-fed wind power generator set. In other words, one kind of the conventional wind power generator sets works in a doubly-fed generation mode, the other works in a full-power mode. In general, the full-power wind power generator set consists of a full-power converter and a full-power generator (e.g., a permanent magnet synchronous generator, an electrical excitation generator, and an induction generator), which has a wider operating range of power generation, a lower cut-in wind speed, and higher power generation efficiency, and good adaptability to a power grid. However, the full-power wind power generator and the full-power converter are expensive. The doubly-fed wind power generator set consists of a doubly-fed induction generator and a doubly-fed converter. Though the doubly-fed wind power generator has a lower price compared with the full-power generator set, the power generation efficiency is relatively poor at low wind speeds. Moreover, the doubly-fed motor has large electricity loss at low rotation speed, and due to the limitation of the operating voltage of transistors in the converter, the doubly-fed wind power generator will be restricted to the operating rotation speed threshold, and thus the doubly-fed wind power generator cannot work at an optimum tip-speed ratio in a low wind speed period, and its operating range of power generation is narrow.